1. Field of the Invention
This invention relates generally to exhaust systems in gas turbine engines and, more particularly, to a support an seal assembly for transpiration cooled, porous metal transition duct liner segments in such exhaust systems.
2. Description of the Prior Art
In some gas turbine engines, a transition duct defines a hot gas flow path from an aft turbine stage of the engine to an exhaust nozzle or other exhaust discharge. To suppress the radiation signature of the engine and/or to maintain the structural integrity of the transition duct, it is known to provide air cooled liners between the duct and the hot gases. Typically, the liners are annular louvered walls supported on and in spaced relation to the transition duct. Cooling air is routed to the space between the liner and the duct at a pressure exceeding the gas pressure in the exhaust gas flow path. The cooling air flows through the louvers and defines a cooling film on the surface of the liner exposed to the hot gases. The louvered construction is structurally advantageous because the louvers readily accommodate thermal growth of the liners. The louvered construction, however, is subject to high cooling airflow rates. As an alternative to the louvered construction, porous metal panels such as disclosed in U.S. Pat. No. 3,584,972, issued on June 15, 1971 to Bratkovich et al. and assigned to the assignee of this invention, may be used as liner segments between the duct and the hot gases and offer the advantage of more efficient use of cooling air. However, because unsealed slots or louvers between the porous metal liner segments must be avoided, supporting the liner segments on the duct and sealing between the edges of adjacent segments while still accommodating thermal growth represents a considerable design challenge. A liner segment support and seal assembly according to this invention represents a novel response to that challenge.